In all itching papular erup-tions, hot dilute solutions of the perchloride are likely to give relief. Trousseau recommends a strength of 12 gr. to the pint, and justly lays stress upon the importance of its being used hot.

In prurigo the ointment of ammoniated mercury either alone, or combined with hydrocyanic acid, or with lead compounds, often gives relief, and calomel ointment is a good remedy for pruritus ani, and for pruritus of the scalp connected with chronic eczema or pityriasis.